Isocamphylcyclohexanols are constituents of the industrially produced sandalwood perfumes, which are composed of synthetic mixtures of various terpencyclohexanol isomers. Industrial sandalwood perfumes replace natural sandalwood oil in soaps, cosmetic products and perfume compounds.
As starting compounds for the isocamphylcyclohexanols, for example, the isocamphylguaiacols can be prepared in a known manner by reacting camphene with guaiacol with the aid of acidic catalysts, for example boron trifluoride and acetic acid; the isocamphylguaiacols are then converted into the isocamphylcyclohexanols by hydrogenation of the aromatic nucleus and cleavage of the methoxy group.
The reactions proceed according to the following equation: ##STR1##
It is already known to hydrogenate alkylation mixtures of camphene and catechol (U.S. Pat. No. 4,014,944) or camphene and guaiacol (DE-A 2 921 139) with hydrogen over Raney nickel to form the desired isocamphylcyclohexanols.
Without exception, these processes of the prior art proceed discontinuously using powdered catalysts by the suspension process.
In the case of powdered catalysts, the following difficulties exist (1) to activate said catalysts in a controlled and uniform manner, (2) to circulate powdered catalysts with the aid of special sludge pumps and (3) to separate powdered catalysts quantitatively from the reaction product. Sludge pumps are, after all, subject to a high mechanical loading. The quantitative removal of powdered catalysts is furthermore expensive because it requires a coarse filtration and a fine filtration using equipment with switching facility. Furthermore there is a great risk that the catalysts quickly lose their activity as a result of these additional operations and therefore furthermore cause high catalyst consumptions. In addition, powdered catalysts can only be loaded to a limited extent and can be freed from the reaction products only with difficulty, which makes their working-up difficult.
The object was therefore to prepare highly loadable, acid-resistant and long-life catalysts for preparing isocamphylcyclohexanols which catalysts should be free of complicated support systems and therefore capable of being worked up again.